DWV Toilet to Sanitary t

I am about to piece together my first DWV waste and vent lines. The bathroom was remodeled and enlarged to accommodate a 6' tub in a new location. Since I want to keep all in check with codes for MD, I have a few questions please.
First off does any one see something terribly wrong with my current set up?
The problem I think I may encounter is the double 3" sanitary t. the water closet drains into a vent elbow which in turn is connected to the double t, from there it all goes 3 south out to the sewer. I plan on using a 1.3 - 1.6 flow toilet. I could use a 3" single t and reroute the kitchen sink to go from a 1.5 and dump into a vertical 3" which will go into a 3" wye if needed.
The picture is for demonstration. This is close to the actual waste configuration, but the pipe lengths have been shortened on the water closet.[/IMG]

The sanitary cross, can be a double combination Y-1/8 bend in your situation, but not necessarily in others. You CANNOT change the combination fitting to a sanitary tee, unless you revise the piping. If you are going to reduce the sink drain, do it AT the "tee", not the elbow. What is the "main stack"?

I will most likely revise the sink to eventually go into a wye just south of the waste (below where double t is).
I am not sure what you mean by "You CANNOT change the combination fitting to a sanitary tee". Please elaborate by using the colors in the photo.

I am trying very hard to do this correctly.
So from my understanding, I can not use sanitary t's on their backs (horizontal position). Would it be OK to replace it with a wye in a horizontal position with a 45 degree fitting or is this essentially the same thing?

I am trying very hard to do this correctly.
So from my understanding, I can not use sanitary t's on their backs (horizontal position). Would it be OK to replace it with a wye in a horizontal position with a 45 degree fitting or is this essentially the same thing?

Thanks,
Rob

Click to expand...

A wye fitting with a 45 elbow is the optimum way to do that fitting. It is NOT the same as the sanitary tee.

Why would you do that. The combo fittings you show are usually easier to work with than "Y"s at those locations. IF the sink is going into the vertical "main vent", and doing so properly, then the sink DOES have a vent. YOU are the one who made the notation, "Note on shower. I will replace the long sweep with a sanitary tee". You CANNOT do that. You have also made the same mistake many people do when they decide that anyone can be a plumber. They think that "bigger is better" when it comes to drain line pipe sizes. You also do not show how you are going to vent the shower using your drain line configuration.